The field of the invention is roofing materials and the invention relates more particularly to a type of roofing material referred to as "roof planking" which is described in detail in applicant's U.S. Pat. Nos. 3,626,439; 3,693,305; and 3,905,165.
Although such roof planking is satisfactory, it was somewhat difficult to force an upper plank into its adjacent lower plank while still maintaining a leak-proof roofing because the distortion of the sealing, resilient material is too great. This becomes critical over such a wide band of sealing material.